lib/other/getttyent.c

   1 /*      getttyent(3) - get a ttytab entry               Author: Kees J. Bot
   2  *                                                              28 Oct 1995
   3  */
   4 #define nil 0
   5 #define open _open
   6 #define close _close
   7 #define fcntl _fcntl
   8 #define read _read
   9 #include <string.h>
  10 #include <sys/types.h>
  11 #include <ttyent.h>
  12 #include <unistd.h>
  13 #include <fcntl.h>
  14
  15 #define arraysize(a)    (sizeof(a) / sizeof((a)[0]))
  16 #define arraylimit(a)   ((a) + arraysize(a))
  17
  18 static char TTYTAB[]= "/etc/ttytab";    /* The table of terminal devices. */
  19
  20 static char buf[512];                   /* Read buffer. */
  21 static char ttline[256];                /* One line from the ttytab file. */
  22 static char *ttargv[32];                /* Compound arguments. */
  23 static struct ttyent entry;             /* Entry to fill and return. */
  24 static int ttfd= -1;                    /* Filedescriptor to the file. */
  25 static char *bufptr;                    /* Place in buf. */
  26 static ssize_t buflen= 0;               /* Remaining characters in buf. */
  27 static char *lineptr;                   /* Place in the line. */
  28 static char **argvptr;                  /* Place in word lists. */
  29
  30 void endttyent(void)
  31 /* Close the ttytab file. */
  32 {
  33         if (ttfd >= 0) {
  34                 (void) close(ttfd);
  35                 ttfd= -1;
  36                 buflen= 0;
  37         }
  38 }
  39
  40 int setttyent(void)
  41 /* Open the ttytab file. */
  42 {
  43         if (ttfd >= 0) endttyent();
  44
  45         if ((ttfd= open(TTYTAB, O_RDONLY)) < 0) return -1;
  46         (void) fcntl(ttfd, F_SETFD, fcntl(ttfd, F_GETFD) | FD_CLOEXEC);
  47         return 0;
  48 }
  49
  50 static int getline(void)
  51 /* Get one line from the ttytab file, return 0 if bad or EOF. */
  52 {
  53         lineptr= ttline;
  54         argvptr= ttargv;
  55
  56         do {
  57                 if (buflen == 0) {
  58                         if ((buflen= read(ttfd, buf, sizeof(buf))) <= 0)
  59                                 return 0;
  60                         bufptr= buf;
  61                 }
  62
  63                 if (lineptr == arraylimit(ttline)) return 0;
  64                 buflen--;
  65         } while ((*lineptr++ = *bufptr++) != '\n');
  66
  67         lineptr= ttline;
  68         return 1;
  69 }
  70
  71 static int white(int c)
  72 /* Whitespace? */
  73 {
  74         return c == ' ' || c == '\t';
  75 }
  76
  77 static char *scan_white(int quoted)
  78 /* Scan for a field separator in a line, return the start of the field.
  79  * "quoted" is set if we have to watch out for double quotes.
  80  */
  81 {
  82         char *field, *last;
  83
  84         while (white(*lineptr)) lineptr++;
  85         if (!quoted && *lineptr == '#') return nil;
  86
  87         field= lineptr;
  88         for (;;) {
  89                 last= lineptr;
  90                 if (*lineptr == 0) return nil;
  91                 if (*lineptr == '\n') break;
  92                 if (quoted && *lineptr == '"') return field;
  93                 if (white(*lineptr++)) break;
  94         }
  95         *last= 0;
  96         return *field == 0 ? nil : field;
  97 }
  98
  99 static char **scan_quoted(void)
 100 /* Read a field that may be a quoted list of words. */
 101 {
 102         char *p, **field= argvptr;
 103
 104         while (white(*lineptr)) lineptr++;
 105
 106         if (*lineptr == '"') {
 107                 /* Quoted list of words. */
 108                 lineptr++;
 109                 while ((p= scan_white(1)) != nil && *p != '"') {
 110                         if (argvptr == arraylimit(ttargv)) return nil;
 111                         *argvptr++= p;
 112                 }
 113                 if (*lineptr == '"') *lineptr++= 0;
 114         } else {
 115                 /* Just one word. */
 116                 if ((p= scan_white(0)) == nil) return nil;
 117                 if (argvptr == arraylimit(ttargv)) return nil;
 118                 *argvptr++= p;
 119         }
 120         if (argvptr == arraylimit(ttargv)) return nil;
 121         *argvptr++= nil;
 122         return field;
 123 }
 124
 125 struct ttyent *getttyent(void)
 126 /* Read one entry from the ttytab file. */
 127 {
 128         /* Open the file if not yet open. */
 129         if (ttfd < 0 && setttyent() < 0) return nil;
 130
 131         /* Look for a line with something on it. */
 132         for (;;) {
 133                 if (!getline()) return nil;     /* EOF or corrupt. */
 134
 135                 if ((entry.ty_name= scan_white(0)) == nil) continue;
 136                 entry.ty_type= scan_white(0);
 137                 entry.ty_getty= scan_quoted();
 138                 entry.ty_init= scan_quoted();
 139
 140                 return &entry;
 141         }
 142 }
 143
 144 struct ttyent *getttynam(const char *name)
 145 /* Return the ttytab file entry for a given tty. */
 146 {
 147         struct ttyent *tty;
 148
 149         endttyent();
 150         while ((tty= getttyent()) != nil && strcmp(tty->ty_name, name) != 0) {}
 151         endttyent();
 152         return tty;
 153 }